We are requesting the purchase of a Bio-Rad MicroRadiance Confocal Imaging System to be shared by NIH-funded researchers in several departments at the Charles River Campus of Boston University. This confocal microscope will extend the research of several Users who are already experienced with confocal microscopy, and it will allow the initiation of many new biomedical research efforts using confocal microscopy by 5 major and 5 minor Users. Their research of the major Users covers a wide range of microscopic applications including the following: visualization of basic cellular events, the analysis of neuronal and synaptic anatomy and function, the subcellular localization of cellular components, the study of development, and cell-specific gene expression. A confocal microscope is critical for studies which require high resolution light microscopic images of fluorescent markers, particularly in thick or living specimens. This request includes a Bio- Rad MicroRadiance Confocal Imaging System that can be interchangeably integrated with either an upright Olympus BX50 or an inverted Olympus IX70 light microscope. The MicroRadiance confocal microscope provides excellent optical performance and allows the simultaneous analysis of single- or double-labeling and transmitted light (Nomarski) images. The lasers we are requesting (a dual-line argon ion and a green helium neon laser) provide three well-spaced excitation wavelengths for the broad range of fluorochromes needed for optimal multiple-labeling. The Lasersharp software is intuitively organized and well-suited for a multi-user facility. All of the confocal settings are totally computer controlled with pre-defined user profiles that can be automatically set for each of the labeling techniques used by a specific user. This software supports all of the optical sectioning, 3-D reconstruction and rotation, and kinetic analysis requirements of the Users. The upright BX50 and the inverted IX70 light microscopes have excellent optical performance, and the combination of these light microscopes and the Bio- Rad MicroRadiance confocal will meet the specific needs of our Users.